Conveying apparatus



2 Sheets-Sheet 1 Filed Sept. 24, 1962 INVENTOR. ALFRED E SANFORD, 1I

ORNE Y5.

Jan. 12, 1965 A. F. SANFORD u 3,165,213

CONVEYING APPARATUS Filed Sept. 24, 1962 2 Sheets-Sheet 2 INVENTOR. ALFRED E SAN FORD, I

United States Patent l 3,165,213 CIBNVEYING APPARATUS AlfredF. Sanford II, Concord, Tenn, assignor to Sanford- Day Gorporaticn, a corporation of Tennessee Fited Sept. 24, 1962, Ser. No. 225,741 5 Claims. (Qt. 2l453) The present invention relates to conveying apparatus and especially to drop-bottom door railway dump cars and track assemblies for use therewith. The invention is more particularly characterized by novel latch-tripping mechanism for realeasing the drop-bottomdoors in a dumping station.

In the art of drop-bottom railway rolling stock'such as mine cars, it is a common practice to provide mine cars having at least one drop-bottom door which is held closed by latching means located ,at the free or rearward edge of the door in protected position relative to the frame structure of the car. Tripping mechanism is provided which is mounted adjacent the trackway in the vicinity of a dumping station, so that as the car passes over the tripping mechanism, the tripping mechanism will trip the latch means to release the door to fall by gravity to an open position, thereby permitting the ladingto fall into the dumping station. When the car has more than one door, the rear door is latch operated and the forward doors are released in series by the opening of therear door, in a Well-known manner.

A number of types of latch-tripping devices have been used in the past. Among the best such devices for general usehasbeen that shown and described in Jones US. Patent No. 2,728,471, December 27, 1955. In the device of that patent, a vertically movable U-shaped loop inclines upward lengthwise of the tracks in the direction of movement of the car, its closed end being uppermost. The crosspiece of this loop at the upper end thereof yieldably bears against the underside of the car passing over the its forward position, the latch supports the rear end of the rear door on a shelf and is provided witha recess lower than the shelf and the crosspieoe of the U-shaped loop engages in this recess as the car moves'forward across the loop. The loop in the recess draws the latch to the v rear under the influence of forward car movement, until the rear edge of the rear door'leaves the shelf of the latch and falls open by gravity. Thereafter, the altered position of the latch coacts with the verticallyyieldable mounting of the loop to cam the loop out of the latch recess so that the car can continue its forward movement unimpeded by the engagement of the loop and the latch.

When the rolling stock and tripping mechanism of such earlier conveying apparatus are fairly new or otherwise in proper operating condition, the tripping mechanism described above works very well. Unfortunately, however, long usage sometimes tends to misalign these mechanisms and to alter the relationship of their parts to each other so that they do not function altogether as intended. Specifically, it occasionally happens that the relationship of the latch and the tripping mechanism to each other will change so that the latch and the tripping mechanism do not disengage from each other quite as soon as intended, with the result that great strain is placed on both the latch and the tripping mechanism. Under these circumstances, either the latch or the tripping mechanism or both can be damaged by the sudden jerk that results from delayed disengagement.

Accordingly, it is an object of the present invention 3,155,213 Patented Earn. 12, 1965 ICC ' to provide dumping conveyances of the drop-bottom door type, including structure for assuring proper disengagement of a drop-bottom door latch and a tripping mechanism therefor.

Another object of the present invention is the provision of conveying apparatus comprising the combination of a trackway and a drop-bottom dumping conveyance movable therealong and a tripping mechanism mounted adjacent the tr-ackway for tripping latch mechanism on the conveyance to open the drop-bottom door thereof, the parts of the combination being so related to each other and characterized by such structure that the tripping mechanism and the latch means will disengage from each other in a, desired fashion afterthe latch hasbeen tripped to open the door.

Finally, it is an object of the present invention to'provide conveying apparatus and dumping convenyances useseful as a part thereof and components of such dumping conveyances which will be relatively simple and inexpen sive to manufacture and install, easy and reliable to operate, maintain and repair, and rugged and durable in use.

Other objects and advantages of the present invention will become apparent from a consideration of the following description, taken in connection with the accompanying drawings, in which:

FIGURE 1 is a side elevation of a conveying apparatus according to the present invention;

FIGURE 2 is an enlarged fragmentary longitudinal sectional view through the structure of FIGURE 1 in the vicinity of thelatch, showing the latch in engaged position immediately prior to a latch-tripping operation;

FIGURE 3 is a fragmentary sectional view on the line 3-3 of FIGURE 2;

FIGURE 4 is a schematic view of a portion of the structure of FIGURE 2, showing the position of the parts immedinately after the latch and the door have been disengaged from each other FIGURE 5 is a view similar to FIGURE 4 but showing a later stage of the latch-tripping operation, at which time the latch and the latch-tripping mechanism have almost disengaged from each other; and

FIGURE 6 is a view similar to FIGURES 4 and 5 but showing a still further stage in the operation of the apparatus, in which thelatch and the latch-tripping mechanism have fully disengaged from each other and the latch is returning to its normal position while the latch-tripping mechanism is passing on beneath the car toward the rear thereof. Y I

Briefly stated, the present invention comprises-the discovery that proper disengagement'of the latch and the latch-tripping device from each other can be assured if the conveyance is provided with cam means mounted thereon closely laterally adjacent the latch means and laterally overlying-the latch means in the rearward position of the latch means and having a forward cam surface that is inclined downwardly rearwardly and which, when the latch is in that rearward position, is disposed farther forward than at least a portion of the latch recess that received the tripping device. In one aspect of the invention, the contacting surface of the cam means forms obtuse angles with the contacting surface of the hook that defines the lowerportio'n of the recess of the latch means when the hook moves to its rearward or disengaging position. In another aspectof the invention, the tripping device contacts a more steeply inclined surface of the cam means during the disengagement of the tripping device from the latch means, and thereafter contacts a less steeply inclined surface of the cam means as the tripping device moves toward the rear of the conveyance. In still another aspect of the invention, the shelf on which the rear of the door rests is laterally offset to one side other side of the hook of the latch, so that the cam and the hook are quite close to each other but at the same time there is no possibility of the cam and the door interfering with each other. Finally,lin another aspect of the invention, the tripping member is the erosspiece carried at the upper end of a leg that is inclined upward in the direc tion of movement of the conveyance along the trackway, and the hook of thelatch and the camare disposed closely adjacent each other but are both spaced a substantial distance from the leg. Preferably, the crosspiece is carried by a pair of legs and is in the form of the closed bottom of a U-shaped loop, in which case both the hook and the cam means are spaced several times farther from each leg than they are spaced from each other.

Referring, now to the drawings in greater detail, and first to FIGURE ,1 thereof, there is shown a drop-bottom mine car 1 which overall may be of conventional construction, mounted for movement on the usual wheels 3 longitudinally extending side sills 7 at either side thereof which are interconnected at their ends by end sills 9 which also provide mountings for the. coupler and bumper assemblies of the cars so that the cars may be interconnected in a train.

.The major portion of the mine car is thus comprised of a lading body bounded by sills 7 and 9 and the side and end walls of the car interconnected therewith. The bottom of the lading body is defined by a series of dropbottom doors 11, 13 and 15 mountedfor vertical swinging movement about horizontal axes extending transversely of the length of the car and disposed at the forward edges of the doors, the door 15 being the rearmost of the three. It will of course be understood that the number of doors is immaterial to the present invention, the present invention being capable of embodiment in cars having plural doors or onlya single door.

Door 15 includes at least one latch bar 17 at its rearmost edge, latch bar 17 resting on a latch 19 which keeps door 15 closed. The forward edge of door 15 supports the rear edge of door 13 and the forward edge of door 13 supports the rear edge of door 11, in a conventional manner. As is also conventional, the doors open in the order 15-13-11, the opening of door 15 releasing the rear edge of door13 and the opening of door 13 releasing the rear edge of door 11. As best seen in FIGURE 2, latch 19 is mounted for swinging movement on a cross shaft 21 carried by the conveyance, the axis of swinging movement of latch 19 being horizontal and transverse to the length of car 1 and rails 5. A coil compression spring 23' acts between a plate 25 that is mounted on and extends forward from rear end sill 9, and a plate 27 which is secured to the top of latch 19. Latch 19 also includes a front plate 29 which is generally upright and disposed in a plane parallel to the axis of swinging movement of latch 19. A

rib 31 is secured both to plate 27 and to plate 29 and is seen in FIGURE 2, this recess being disposed a lower level than surface 37. i

The latch mechanism has been described thus far in connection with one latch 19. It .will be understood, how ever, that the number of latches is immaterial to the invention. Indeed, it is preferred that two latches 19 be employed, one on either side of the longitudinal center line of the conveyance. Thus, door 15 in the preferred form of the invention is supported on two latch bars 17.

It will therefore be appreciated that FIGURE 2 is'a view 'be another latch assembly on the near side of the'assembly shown in FIGURE 2, which is to say'that there will be another latch assembly to the right of the assembly shown in FIGURE 3. The two latch assemblies and the associated structure are mirror images of each other on either side of the vertical plane of the longitudinal. center line of the conveyance. I

Referring again to FIGURE 1, a tripping mechanism is mounted adjacent the trackway and preferably between rails 5 thereof. There will preferably be a tripping mechanism 45 for each latchassembly, so that in the preferred embodiment there will be two such tripping mechanisms- Of course, if both latches 19 are rigidly mounted on a single shaft 21, then only one tripping mechanism is needed for a plurality of latches 19. The tripping mechanism' of the illustrated embodiment is shown in greater detail in the above-identified Jones patent and need be described in the present application only in broad outline, reference for further details'being had to that patent.

Each tripping mechanism 45 comprises a pair of parallel arms 47 mounted for rotation at their lower forward ends on a shaft 49 the axis of which is fixed relative'to the trackway. A U-shaped loop 51 is mounted on the upper rear ends of arms 47 and comprises a pair of straight parallel legs that are inclined upward in the direction of conveyance movement along the trackway and which terminate at their upper ends and are there interconnected by a straight crosspiece 55 that is horizontal and perpendicular tothe direction of travel of theconveyance along the trackway. At their lower rear ends, a shaft 57 mounts loop 51 on arms 47 for vertical swinging movement abouta horizontal axis parallelto theaxis of shaft 49. Arms 47 are thus vertically swingable about shaft 49, while loop 51 is vertically swingable relative to arms disposed in a vertical plane parallel to the length of car 1 and track 5. Adjacent its lower end, rib 31 on one side thereof carries a metal block in the form of a shelf 33, and on its other side rib 31 carries a hook plate 35 that is inclined downward in the direction of movement of the conveyance along the track.

Shelf 33 has an upper surface 37 which is generally horizontal in the position shown in FIGURE 2 and which in that position providesa shelf on which latch bar 17 rests by gravity to hold door 15 closed. Shelf 33 also has a forward lower surface 39 that inclines upward in the direction of conveyance movement along thetracks. Hook plate 35 has a forward upper surface 41 that inclines downward in the direction of vehicle movement along the tracks. and that terminates downward. in a rounded end 43.. Even though, they are not in vertical alignment with eachother, surfaces 39 and 41; thus define the respectively upper and lower sides of a forwardly opening recess as ing between a fixed abutment and a member rigid with loop 51 continuously urges loop'51 clockwise as seen in FIGURE 1. In this way, means is provided continuously yieldably urging crosspiece 55 upward. A lever 63 interconnected with the linkage just described permits retraction of crosspieceSSdownward when it is not desired to tripa latch 19.

Thus far, the structure described andits operation may be conventional. Thus, as a loaded conveyance with door 15 held closed by latch 19 approaches the dumping station, loop 51 is engaged and pushed down by the under portions of the conveyance and crosspiece 55 yieldably scrapes along 'the bottom of the conveyance until it reaches the rear endof door 15, whereupon it rises under the influence of springs 59 and 61 to such height thatit enters into the recess defined by surfaces 39 and 41 of shelf 33 and hook plate 35, respectively. In that recess, in contact with surfaces 39 and 41 as seen in FIGURE 2, crosspiece'55'thus. engages and pulls to the rear latch 19 about the axis of shaft 21, whereupon surface .37 of shelf 33 moves to the rear in sliding contact with. the rear. lower end of latch bar 17, until latch bar 17 clears shelf33 and the weight of the lading on door 15 causes door 15 and latch bar 17 to fall rapidly about the axis of vertical swinging movement of the door at the forward end thereof.

As the conveyance continues its forward movement, latch 19 is drawn sufficiently far to the rear and rotated counterclockwise about shaft 21 to the extent that crosspiece 55 slides downward along surface 41 of hook plate 35 and about rounded end 13 and latch 19 and loop 51 thus disengage from each other. During the course of this disengaging movement, latch 19 moves counterclockwise against the influence of spring 23, and preferably crosspiece 55 also moves downward against the influence of springs 59 and 61.

Upon disengagement of latch 19 and loop 51 from each other, spring 23 urges latch 13 clockwise back to the position of FIGURE 2. Thereafter, as the car leaves the dumping station, the usual cams fixedly mounted adjacent the trackway engage doors 11, 13 and 15 in that order and close them, the closing of door 13 thereafter holding door 11 in place, and the closing of door 15 thereafter holding door 13 in place, in the well-known manner. When door 15 closes, lat-ch bar 17 engages forward lower surface 39 of shelf 33 thereby camming latch 19 to the rear as latch bar 17 rises. When latch bar 17 has risen above the level of surface 37, latch 11 swings back clockwise into the position of FIGURE 2, and latch bar 17 comes to rest on upper surface 37. The car is then ready to be loaded again. In the event it is desired selectively to open the dropbottom doors at a location away from a dumping station, conventional means are provided for selectively withdrawing latch 19, in the form of a manual release bar 65 secured to latch 19 onthe underside of plate 27 and extending rearward through a slot 67 in the forward wall of rear end sill 9. A vertical link 69 interconnected with the rear end of bar 65 may be raised when it is desired selectively to release latch 19. Also, the contact of bar 65 with the bottom of slot 67 stabilizes latch 13 in the position of FIGURE 2 so that latch 19 does not swing farther clockwise under the influence of the weight of the lading as transmitted to latch 19 through latch bar 17.

As pointed out above, however, latch 19 and crosspiece 55 do not always smoothly disengage from each other. Accordingly, means are provided for assuring proper disengagement, in the form of a cam plate 71 secured to and extending forward from the front wall of rear end sill 9 at the bottom thereof. Cam plate 71 is disposed in a vertical plane extending lengthwise of the conveyance and its path of travel and is disposed quite close to but spaced from hook plate 35 on the side of hook plate 35 opposite shelf 33. Preferably, cam plate 71 is no thicker than need be to achieve the requisite strength. Thus, for latch 19 that might have a width of hook plate 35 of, say 1 /2 incl1es a thiclmess of rib 31 of, say, A inch, and a width of shelf 33 of, say, 2% inches, cam plate 71 might for example be inch thick and be spaced A; inch from hook plate 35.

Cam plate 71 is also characterized by cam faces which are the lower forward faces of the cam plate. An upper portion of the cam platehas as its cam face a relatively more steeply inclined face 73, and has for its lower portion a relatively less steeply inclined face 75. Cam faces 73 and 75 join at a shoulder 77, it being understood, however, that faces 73 and 75 need not be straight and need not join at a distinct shoulder, but can be rounded and still perform all the functions of the present invention. The inclinations of cam faces 73 and 75 to the horizontal in the illustrated embodiment, might, for example, be about 65 and about 12, respectively.

The sequence of operation by which cam plate 71 assures this engagement of the tripping mechanism and the latch is shown in the series of FIGURES 2, 4, 5 and 6. As seen in FIGURE 2, when crosspiece, 55 first engages in the recess therefor provided by shelf33 and hook plate 35 and bounded by surfaces 33 and 41 of those members respectively, cam plate 71 is Well to the rear of that recess. However, as crosspiece 55 draws latch 19 counterclockwise to the rear, the profile of more steeply inclined cam face 73 impinges on the rear of the latch hook recess, as seen by comparison of FIGURES 2 and 4. When cam face 73 becomes tangential to the contour of crosspiece 55, the pressure theretofore exerted by crosspiece 55 upon surface 39 ofshelf 33 is transferred to cam face 73 along with a portion of the force theretofore exerted by cross piece 55 on surface 41 of hook plate 35. Cam plate 71 relieves a portion of the force on hook plate 35, because cam face '73 is disposed at an obtuse angle to surface 41 at the line of contact between crosspiece 55 and surface 41 and between crosspiece 55 and surface 73. Indeed, throughout the time that crosspiece 55 is in contact both with cam face 73 and with'surface 41, the planes of tangency of crosspiece 55 atthe lines I of contact with face '73 and surface 41 are disposed, at

angles to each other which are greater than Moreover, as latch 1 19 continues to swing counterclockwise, the angle between cam face 73 and surface 41, measured as described above, increases so that as cam plate 71 at least initially moves into the recess theretofore occupied solely by crosspiece 55, an increasing portion of the load theretofore borne by hook plate 35 is transferred to cam plate 71.

This relationship of cam face 73 and surface 41 relative to each other is an important feature of the present invention, for it assures in the first place that hook plate 35 will share the load of crosspiece 55 with cam plate '71. This means that cam face 73 can be desirably steep and can thus definean obtuse angle with surface 41 of hook plate 35, without at the same time making cam plate '71 so thick that it could bear a great portion or even all of the load imposed by crosspiece 55. As a result, cam plate 71 can be made desirably thin; and this desirable thinness of cam plate 71 enables cam plate 71 to be spaced a correspondingly great distance from either leg 53 of loop 51. The assembly of book plate 35 and cam plate 71 can therefore be made of relatively short extent transversely of the direction of vehicle travel, so that a desirably wide spacing from either leg 53 of loop 51 is achieved. This Wide spacing from legs 53 assures correct functioning of the tripping mechanism even though the car may be slued relative to the trackway to such an extent that hook plate 35 and cam plate 71 are disposedto one side or the other of their normal position. In the second place, the increase of the obtuse angle between cam face 73 and surface 41 as cam plate 71 proceeds farther into the recess upon counterclockwise swinging of latch 19 also assures that the force applied by crosspiece 55 to cam plate 71 will increase progressively and will not be applied to cam plate 71 as a sudden shock such as might call for a thicker cam plate 71. p I

Another feature of the invention is the relationship of shelf 33, hook plate 35, and cam plate 71 to each other, with shelf 33 and cam plate 71 in effect spaced apart by hook plate 35. This arrangement assures that the members on the conveyance that share the load of crosspiece 55 will always be next to each other: first shelf 33 and hook plate 35, and then hook plate 35 and cam plate 71. This arrangement also assures that there will be no interference between latch bar 17 and cam plate 71 when the former falls upon door opening movement, for the two will be laterally spaced apart by at least a portion of the width of hook plate 35.

During the progressive entry of cam plate 71 into the hook recess at the lower end of the latch, crosspiece 55 first contacts more steeply inclined cam face 73; and for this purpose, cam face 73 is disposed at about the level of the recess. Crosspiece 55 then moves downward to the rear along cam face 73 until crosspiece 55 clears rounded end 43. Preferably, this clearance occurs about at shoulder 77. Latch 19 is then free to'and does snap 7 back into the position of FIGURE 2, which is also the position it is approaching in FIGURE 6.

A further aspect of the invention is that cam plate 71 also reduces the drag of U-shaped loop 51 on cam plate may be steeply inclined because the load imposed on it is shared by the hook of the latch. Indeed, the steep inclination of face 73 is an advantageous feature of the invention in that it provides the obtuse angular relationship described above between face 73 and surface 41. At the immediately subsequent position of the parts, however, as seen for example in FIGURE 6, cam plate 71 performs an entirely different function of directing crosspiece 55 below the oncoming vehicle structure, and in doing so crosspiece 55 exerts the least 'possible'drag on cam face 75, because cam face 75 is at the smallest-possible angle to legs 53. That this latter drag on cam plate 71 be minimized is important when it is realized that when crosspiece 55 is in contact with cam face 75, hook plate 35 is no longer available to share the load and the entire force of crosspiece 55 on the vehicle is borne by cam face 75. 7

From a consideration of the foregoing disclosure, it will be obvious that all of theinitially recited objects of the present invention have been achieved.

Although the present invention has been described and illustrated in .connection with a preferred embodiment, it is to be understood that modifications and variations may be resorted to without departing from the spirit of the invention, as those skilled in this art will readily understand. Such modifications and variations are considered to be within the purview and scope of the present invention as defined by the appended claims.

What is claimed is:

i 1. In a dumping conveyance adapted to move along a trackway and having a lading body with a drop-bottom door and latch means movable between a forward po-' mechanism moves downward in sliding contact with a forwardly downwardly inclined surface of the latch means that defines the lower portion of said recess to disengage the tripping mechanism from-the latch means to permit continued forward movement of the conveyance;

the improvement comprising: cam means mounted on the conveyance (a) closely laterally adjacent the latch means (b) laterally overlying the latch means in said rearward position of the latch means (c) having, at the level. of a rear portion of said recess, a forward cam surface that is (l) inclined downwardly rearwardly (2) disposed fartherforward than at least a portion of said recess in said rearward position of the latch means a (3) disposed at obtuse angles to said surface of the latch .means as the latch means nears said rearward position thereby to contact and cam, a said vertically movable portion of a tripping mechanism downward out of engagernent with said surface of the latch means immediately after rearward movement of the latch means has released the door to fall open.

2. In a dumping conveyance adapted to move along a trackway and having a lading body with a drop-bottom door and latch means movable between a forward position in. which the latch means maintains therdoor closed and a rearward position in which the 'door is free to fall open, the latch means having a shelf on which a rear portion of the door rests and a forwardly opening recess lower than the shelf for the reception of avertically movable portion of a tripping mechanism adjacent the trackway to move the the latch means to said rearward position whereupon said portion of the tripping mechanism moves downward in sliding contact with a forwardly downwardly inclined surface of the latch means that defines the lower portion of said recess to disengage the tripping mechanism from the latch means to permit continued forward movement of the conveyance;

the improvement comprising: cam means mounted onthe conveyance (a) closely laterally'adjacent the latch mean (b) laterally overlying the latch means in said rearward position of the latch means (c) having a forward cam surface that (1) is inclined downwardly rearwardly (2) includes an upper forward cam face: that is (aa) inclined at. a relatively large'angle to the horizontal (bl disposed farther'forward than at least a portion of said recess in said' rearward position of the latch means 7 (cc) adaptedslidably to contact a, said vertically movable portion of a tripping mechanism during at least a portion of the latchdisengaging movement of the latter (3) includes a lower rear cam face that is inclined at a relatively small angle to the horizontal thereby to contact and cam a said vertically movable portion of a tripping mechanism downward out of engagement with said surface of the latch means immediately after rearward movement of the latch means has released the door to fall open.

3. In a dumping conveyance adapted to move along a trackway and having a lading body with a drop-bottom door and latch means movable between a forward position in which the latch means maintains the door closed and a rearward position in which the door is free to fall open, the latch means having a shelf on which a rear portion of the door rests and a forwardly extending hook lower. than the shelf for engagement with a vertically movable. portion of a tripping mechanism adjacent the trackway tomovethe latch means to said rearwardposition whereupon said portion of the tripping mechanism moves downward in sliding contact with a forwardly downwardly inclined surface of the hook to disengage the tripping mechanism from the latch means to permit continued forward movement of the conveyance, at least a portion of the shelf being laterally offset a substantial'distance to one side of the hook;

the improvement comprising: cam means mounted on the conveyance (a) closely laterally adjacent the latch means (b) on the side of the hook opposite said one side to which the shelf is oifset' I (c) laterally overlying the latch means in said rearward position of the latch means (d) having, at the level of an upper portion of said surface of the hook, a forward cam surface that is 1) inclined downwardly rearwardly (2) disposed farther forward than at leasta portion of said surface of the hookin said rearward position of the latch-means .9 thereby to contact and cam a said vertically movable portion of a tripping mechanism downward out of engagement with said surface of the hook immediately after rearward movement of the latch means has released the door to fall open.

4. Conveying apparatus comprising in combination (A) a trackway (B) a tripping mechanism (1) mounted adjacent the trackway (2) having a vertically movable crosspiece disposed transversely of the length of the trackway (3) having at least one leg (a) inclined upward in one direction lengthwise of the trackway (b) carrying said crosspiece at its upper end (C) a dumping conveyance movable in said one direction along the trackway and including (1) a lading body (2) a drop-bottom door for the lading body (3) latch means (a) movable between a forward position 'in which the latch means maintains the door closed and a rearward position in which the door is free to fall open (b) having a forwardly extending hook having a recess in Which the crosspiece engages to eifect said rearward movement of the latch means at which time said hook is spaced a substantial distance from said at least one leg (4) cam means mounted on the conveyance (a) closely laterally adjacent the latch means (b)laterally overlying the latch means in said rearward position of the latch means (0) spaced a substantial distance from said at least one leg when the crosspiece contacts said hook (d) having, at the level of an upper portion of 1 said hook, a forward cam surface that is (i) inclined downwardly rearwardly (ii) disposed farther forward than at least a portion of said hook recess in said rearward position of the latch means whereby the crosspiece contacts the hook to effect said rearward movement of the latch means without interference between said at least one leg and either of the hook and said cam means. 7

5; Conveying apparatus as claimed in claim 4 wherein said at least one legis a pair of parallel legs carrying and interconnected by the crosspiece at their upper ends, said hook being disposed between said legs when the crosspiece contacts said hook, and saidhook and cam means being spaced from both said legs distances substantially greater than the distance between said hook and cam means when the crosspiece contacts said, hook.

References Cited in the file of this patent UNITED STATES PATENTS Jones Dec. 27, 1955 

1. IN A DUMPING CONVEYANCE ADAPTED TO MOVE ALONG A TRACKWAY AND HAVING A LADING BODY WITH A DROP-BOTTOM DOOR AND LATCH MEANS MOVABLE BETWEEN A FORWARD POSITION IN WHICH THE LATCH MEANS MAINTAINS THE DOOR CLOSED AND A REARWARD POSITION IN WHICH THE DOOR IS FREE TO FALL OPEN, THE LATCH MEANS HAVING A SHELF ON WHICH A REAR PORTION OF THE DOOR RESTS AND A FORWARDLY OPENING RECESS LOWER THAN THE SHELF FOR THE RECEPTION OF A VERTICALLY MOVABLE PORTION OF A TRIPPING MECHANISM ADJACENT THE TRACKWAY TO MOVE THE LATCH MEANS TO SAID REARWARD POSITION WHEREUPON SAID PORTION OF THE TRIPPING MECHANISM MOVES DOWNWARDLY IN SLIDING CONTACT WITH A FORWARDLY DOWNWARDLY INCLINED SURFACE OF THE LATCH MEANS THAT DEFINES THE LOWER PORTION OF SAID RECESS TO DISENGAGE THE TRIPPING MECHANISM FROM THE LATCH MEANS TO PERMIT CONTINUED FORWARD MOVEMENT OF THE CONVEYANCE; THE IMPROOVEMENT COMPRISING: CAM MEANS MOUNTED ON THE CONVEYANCE (A) CLOSELY LATERALLY ADJACENT THE LATCH MEANS (B) LATERALLY OVERLYING THE LATCH MEANS IN SAID REARWARD POSITION OF THE LATCH MEANS (C) HAVING, AT THE LEVEL OF A REAR PORTION OF SAID RECESS, A FORWARD CAM SURFACE THAT IS (1) INCLINED DOWNWWARDLY REARWARDLY (2) DISPOSED FARTHER FORWARD THAN AT LEAST A PORTION OF SAID RECESS IN SAID REARWARD POSITION OF THE LATCH MEANS (3) DISPOSED AT OBTUSE ANGLES TO SAID SURFACE OF THE LATCH MEANS AS THE LATCH MEANS NEARS SAID REARWARD POSITION THEREBY TO CONTACT AND A CAM A SAID VERTICALLY MOVABLE PORTION OF A TRIPPING MECHANISM DOWNWARD OUT OF ENGAGEMENT WITH SAID SURFACE OF THE LATCH MEANS IMMEDIATELY AFTER REARWARD MOVEMENT OF THE LATCH MEANS HAS RELEASED THE DOOR TO FALL OPEN. 